Nicolino "El Intocable" Locche. A lot of people think his nickname means "into-cable" as in "into the cable" like electricity. But that is not true. It means something in English that's not that. It means "The Man Who Kicks Like A Mule But With His Fists Not His Mule Feet/Hooves." And that is exactly what I would expect from this Mexican destroyer. He would tap. that. behind. Floyd would honestly not even know he was being punched out. And then it'd be too late when he found out.
In ONE round? Nobody. You are not KOing a guy as slick as Floyd when he's fresh as a daisy and full of energy at the opening bell. Gun to my head I'd say Hearns if he comes out swinging like he did against Hagler but even then, I can't see him getting the job done in just 1 round Floyd likely gets dropped and blocks, runs, and hugs like a groupie at a concert until the bell rings.
Technically, an Ancient Greek boxer could do it, since there were no rounds. I doubt even a LPR boxer could do it in 1, considering Floyd would just take a knee and have 30 secs recovery plus 10 secs coming to scratch. Maybe Battling Nelson in 1900s ruleset with approved fouls stipulation? Ridiculously abstract but I can't even see Duran or Hearns doing it in 1. Guys like Barbados Joe etc have the power but I don't see 1 round even in the old rulesets.
Hearns has an Outside chance because his unique dimensions and blazing handspeed. If Tommy gets Floyd uncomfortable and backing i could see that scenario. For most others I think going all out for a 1st round KO would be playing into Mayweather's hands.
Jock McAvoy, 5'9" tall, near enough the same size, as were most the 40s middleweights, where Floyd would have been fighting if he lived then. just as Floyd weighed 160 plus when he wasn't fighting, like 'most' fighters today are 1 or 2 Divisions heavier than they actually compete at. so, at eitherside of 5'9" tall and eitherside of 160lbs plus, there are a ton of them over the years.
Basically, he was a 168 or 175 who dried out to 154. He didn’t show much respect for opponents and could throw 100+ punches per round. He could maybe bum rush Floyd and catch him with a weird temple shot and then force a tko by letting his hands go. I wouldn’t bet on it, but it’s a better chance than just about anyone. I don’t see the one shot artists having success.